In short, there are people leaving negative reviews on your map listings. Then shortly after, they are emailing you and offering to remove the negative reviews for a fee. On the other hand, there are people offering this as a service, add negative reviews to your competitors for a fee.

A senior WebmasterWorld member, said:

This has happened to two companies that I work for in the past 6 months. Wondering if anyone else has seen the same...

A bunch of negative reviews are posted in Google Maps for a particular company. About a month after the posts, the company gets a call and is told that the negative reviews can be removed for a fee... typically $400. We have been flaging the reviews, tey it seems to take google forever to even take a look.